Resistor grid



Aug. 26, 1958 A. VAN DER PERK RESISTOR GRID Filed July lO, 1956 f n p p 1J Ej;

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WM mE 6 7 W Dl DH MEW il!! M fl: v d Y TB Rw E B A ATTORNEYS RESISTUR GRH) Albert van der Perk, Rotterdam, Netherlands Application litaly 10, 1956, Serial No. 597,044

1 Claim. (Cl. 21H-69) The invention relates to a resistor for great current, consisting of an upright zigzag shaped strip of resistance material clamped between corrugated metallic clamping strips insulated by corrugated strips of insulating material. Such resistors are applied e. g. as starting-resistance for motors, such as for traction, roller mills and cranes.

From the British patent specification 274,560 such a resistor is known in which, however, the resistance material is enclosed in the clamping material at the place of txation, whereas the British patent specication 252,496 discloses a resistor in which the clamping members are rather complicated, these members enclosing the resistance strips over a large surface at the place of fixation.

It has appeared that with such resistors deciencies, or failures mostly occur exactly at the place of fixation, where the resistance material and the insulating material are pressed together, mainly owing to two causes:

(l) The cooling or heat delivery at this place is at its worst, owing to which here the highest temperatures may occur.

(2) At this place the resistance material and the insulating material are pressed upon each other with a relatively large surface. The condensation moisture from the atmosphere will collect here by the capillary action, owing to which the strong corrosion at this place can be explained, which again will aggravate what is mentioned under 1).

The invention aims at removing these drawbacks and experiments have shown a substantial increase of the duration of life of the resistance packet.

The resistor according to the invention is mainly characterized in that the corrugations in the strips are of insulating material and those in the metallic clamping strips so shallow that the strips of insulating material are in contact with same merely at the edges of the zig-zagshaped strip.

It be remarked that such a fixation with an upright transmitting coil shaped as a at spiral, for a radiotransmitter for maintaining the correct mutual position of the turns, is known from the German patent specication 285,424. With such coils, however, the above mentioned phenomena do not occur, because with such applications there is no appreciable heating resulting in losses.

The invention will be elucidated by the drawing. Fig. 1 is a side view of a resistor element according to the invention, Fig. 2 being a horizontal section over the line II-II of Fig. 1.

tes Brent The resistor according to the invention is made of a number of wires 1.of adequate material brought into a at shape e. g. by rollers. These wires or strips are bent upright to a suitable zig-zag shape, as appears from the drawing.

This grid may as well be cast in an upright position from a suitable resistance material. In this form the desired number of resistance bodies are united to a packet by means of cross-wise extending insulated bolts 2 with nuts 3.

From Fig. 2 appears that the small sides of the upright wound resistor element 1 at both sides are surrounded by a strip of mica 4 or similar insulating material, at the external sides of which strips 5 are provided. These metallic strips are corrugated, as appears from Fig. 2 and when compressing the packet the mica strips 4 as well will take a corresponding wave-shape. In this manner it is attained that the contact surface between the resistor element 1 and the mica strips 4 becomes very small, whilst by the wave-shape of the strips 4 and 5 a shift and deformation of the resistor elements is prevented and ample air channels are formed around the parts of these elements, for the purpose of cooling.

Against the metal strips 5 metal strips 6, 7 lie, against which at the end of the resistance packet a metal pressing element 8 joins, which is clamped by the nuts 3 with the intermediary of rings 9.

As spacers between the various resistor elements 1 metal strips 10 serve which are bent around the bolts 2 and extend over the entire width of the packet. The mutual connection of the various resistor elements 1 may occur in a known manner, e. g. by means of strips 11 which may be provided with connecting terminals 12.

The dimensions of the packets may be arbitrary in which at great height of the packets the clamping may occur by means of the described means at a number of places distributed over the height.

I claim:

A resistor for heavy current comprising a zig-zag shaped metallic ribbon having spaced portions with edges lying substantially in a plane and the ribbon surfaces essentially normal to that plane, a corrugated metallic sup-` port, said corrugations corresponding to the spacing of said portions, an insulating strip intermediate said ribbon and said support and generally conforming to said corrugations, and means to clamp the edges of -said spaced portions in the corrugations of said support, said corrugations, being shallow whereby the contact surfaces between said ribbon and the insulating strip are limited to the edges of the ribbon.

References Cited in the file of this patent UNITED STATES PATENTS 1,006,655 Harris Oct. 24, 1911 1,226,627 Barnum May 22, 1917 2,518,941 Satchwell et al. Aug. 15, 1950 FOREIGN PATENTS 285,424 Germany .lune 30, 1915 252,496 Great Britain lune 3, 1926 274,560 Great Britain July 21, 1927 648,494 France Dec. 10, 1928 969,907 France July 26, 1948 

